I could try to say: then don't take a piss while watching... 
I've read about problems with PowerDVD and hybernation. Are the comps with a prob on different power settings than the others? Try to not let it go to hybernation or try to change the power off settings. Are they maybe in different powermode settings (for laptops maybe)?
Also, what's more similar between the ones that have the problem and the ones that don't? Both same processor? Same keyboard (the ones with power/hybernation buttons on it)? Same casings with power buttons?
I myself use VLC by the way. Which can also grab frames.

I've read about problems with PowerDVD and hybernation. Are the comps with a prob on different power settings than the others? Try to not let it go to hybernation or try to change the power off settings. Are they maybe in different powermode settings (for laptops maybe)?
Also, what's more similar between the ones that have the problem and the ones that don't? Both same processor? Same keyboard (the ones with power/hybernation buttons on it)? Same casings with power buttons?
I myself use VLC by the way. Which can also grab frames.